Sewage aerator



D. S. M LAREN SEWAGE AERATOR Sept. 10, 1968 Original Filed May 25, 1966M Q W NC T v M M m 4 5 5 MM w a M MM,

1 MC 5 a fl J Q United States Patent 3,400,918 SEWAGE AERATOR David S.MacLar-en, 21176 Bantley Road,

Shaker Heights, Ohio 44120 Confinuation of application Ser. No. 552,829,May 25, 1966. This application Mar. 8, 1967, Ser. No. 621,648 5 Claims.(Cl. 261-87) ABSTRACT OF THE DISCLOSURE A sewage aerator including atreatment tank with a covered enclosure located on top thereof. A sealedcasing or housing is mounted in the enclosure and an electric motor witha stator and rotor is positioned therein. A motor shaft is rotatablymounted on bearings in the upper and lower end walls of the motor casingand has a lower extension which extends beyond the surface of sewage inthe tank. An axially extending passage is provided in the shaft andextension and conduit means connect the upper end of the passage toatmosphere. Aspirator tubes which extend in a radial direction connectthe lower end of the passage to the interior of the tank and uponrotation of the shaft cause an aspirating effect to draw air down thepassage and into the tank. Screw means on the shaft serve to agitate thesewage.

This application is a continuation application of US. Ser. No. 552,829filed May 25, 1966, entitled, Flood-Proof Sewage Aerator, now abandonedin favor of this application.

This invention relates to gas and liquid contact apparatus, andparticularly to mixing and aerating apparatus for use in the treatmentof sewage by the activated sludge process.

The primary object of the invention is to provide a flood-proof sewageaerator, for use in the treatment of mixed sewage liquors by theactivated sludge process, that is an improvement over the mixing andaerating unit described in US. Patent No. 2,928,661, to Albert S. Mac-Laren, issued Mar. 15, 1960.

Another object is to provide a sewage mixing and aerating device whoseair-intake opening is elevated above the top wall of the treatment tankin which the device is mounted, so that its air supply is not affectedby a rise of the liquid level in the tank.

Still another object is to provide a device of the type stated having anelectric motor with a hollow shaft, whose air-intake path travelsdirectly through the hollow shaft of the driving motor, so that cool airconstantly passing through the shaft serves as a heat absorbing medium,for lowering the operating temperature of the motor.

A further object is to provide such a device, whose constructionprevents the bearings which support its hollow, air conducting, motorshaft from becoming corroded or damaged due to water vapor condensation,or water seepage.

These, and other objects of the invention will become apparent from areading of the following specification and claims, together with theaccompanying drawing, wherein like parts are referred to and indicatedby like reference numerals, and wherein:

FIGURE 1 is a side elevation, partly in section, showing the flood-proofsewage aerator, that is the subject of this invention, as it appearsmounted in a secondary sewage treatment tank; and,

FIGURE 2 is a vertical sectional view of the unit in its un-mountedcondition.

Referring more particularly to the drawing, there is seen in FIGURE 1the flood-proof sewage aerator that is the subject of this invention,broadly indicated by reference numeral 10, as it appears mounted in asecondary sewage tank 17. The tank 17, of which. only the roof is shown,is made of concrete and is similar in construction to that described inUS. Patent No. 2,852,140 to Albert S. MacLaren, issued Sept. 16, 1958.

Reference numeral 18 indicates a man hole collar, having a verticallyextending crock 15 cemented therein. A cover 19 serves as a closure forthe collar. A conventional mushroom type airbreather 20 is mountedthrough the cover.

Reference numeral 53 indicates the surface of the mixed sewage liquorsundergoing treatment in tank 17.

The unit 10 is removably and rigidly suspended in a vertical planewithin the crock 15 by means of 3 equi-spaced legs 14, having upper feet12 which rest upon the shoulder 16, of crock 15, and lower feet 13 whichbear against the cylindrical wall of the crock, to hold the unit in avertical plane.

As seen in FIGURE 2, the device comprises a liquidtight electric motorcasing, having a cylindrical side wall 11 and upper and lower end wall,or closure caps, 23 and 22, respectively, joined thereto throughliquid-tight sealing gaskets 51 and 52, respectively.

Reference numeral 35 indicates an electric motor stator, mounted in thecasing.

The upper and lower end walls, or closure caps, 23 and 22, respectively,have axially aligned motor shaft bores 27 and 24, respectively, centeredtherethrough.

A sealed, permanently lubricated, ball-bearing 28 is mounted in theupper shaft bore 27, and a similar ballbearing 26 is mounted in thelower shaft bore 24. A conventional, rotary ceramic-carbon, shaft seal25 is located outboard of the lower shaft bearing 26.

Reference numeral 40 indicates a hollow motor shaft rotatably supportedwithin the casing thru the bearings 26 and 28. A motor rotor 36 ismounted on and carried by the shaft 40.

Power is brought to the motor cable 50, from the outside, through aconventional hermetic connector, not shown, since it forms no part ofthe invention.

An oil-filler plug 38 is located in the top closure cap 23. The motorcasing is filled with transformer oil 37 to completely submerge thestator 35 and rotor 36. The oil acts as both a cooling or heat-transfermedium and a lubricant. Space is left at the top of the casing to allowfor expansion of the oil.

As seen in FIGURE 2, the upper end 29 of the upper shaft bore 27 isthreaded to receive the threaded end of an air-inlet plug 30. The plug30 has a blind bore 31, of a diameter to fit snugly over the upper endof the hollow shaft 40.

Reference numeral 33 indicates a dependent nose centered in the blindbore 31 and adapted to extend downwardly into the hollow shaft 40, andof a diameter to clear the inner wall thereof.

An upstanding nipple 34 is positioned on the plug 30 in axial alignmentwith the nose 33. Reference numeral 32 indicates an axial bore in theplug 30 extending through the nose and nipple.

A conventional mushroom type intake breather 20, having the usual airfiltering screen, is mounted through the manhole cover 19, as seen inFIGURE 1.

A flexible hose 21 mounted on the nipple 34 connects the air-inlet plugbore 32 with the breather 20.

The lower end portion of the shaft 40 extends downwardly through theclosure cap 22 of the casing and projects below the surface 53 of themixed sewage liquors, as again seen in FIGURE 1. While the shaftillustrated is composed of two sections, 40 and 41, joined end-to-endthrough a sleeve 42 having locking set screws 43, it is to be understoodthat the shaft might be fabricated from a 3 single length of tubing. Thelower end of the shaft 40-41 is closed by means of a plug 54.

A three blade screw-propeller 47 is mounted on the shaft 40-41 so thatit will be approximately 8 below the sewage surface 53 when the unit 10is positioned as seen in FIGURE 1.

A second, identical, propeller 48 is mounted proximate the lower end ofthe shaft 4041, approximately 8" below the upper propeller 47. Thedistance between the upper and lower propellers is calculated to be suchthat the lower propeller 48 will pick up the first propeller columnatedstream.

Reference numerals 45 and 46 indicate two diametrically alignedaspirator tubes mounted through the wall of the hollow motor shaft 4041,and open to the interior thereof.

Reference numeral 44 indicates a foam breaking disk which is mounted onthe shaft sleeve 42, as is seen most clearly in FIGURE 2. The disk actsto beat down and break up any foam which might accumulate in the crockand try to creep up the shaft 40-41 into the bearings and motor.

In operation, the motor shaft 4041 rotates at a speed of approximately1750 rpm.

The rotating propellers create a high velocity columnated stream in theliquid sewage which extends from near the surface 53 in a perpendiculardirection directly downward-to the floor of the tank 17. The highvelocity stream from the upper propeller 47 is caught up by thepropeller 48 and given additional impetus in its travel toward the tankfloor, so that a shaft 4041 extending approximately only half the liquiddepth is adequate to deliver the stream to the tank floor.

At the same time the high speed rotation of the aspirator tubes 45 and46, carried by the shaft 4041, produces cavitation, in the sewageliquid, at their trailing faces, thereby creating a partial vacuum inthe hollow shaft 40-41.

In response to natural physical laws, atmospheric air will then flowthrough the breather 20, hose 21 and bore 32 of the stationary plug nose33, into the rapidly rotating hollow shaft 40-41, and out the open endsof the aspirator tubes 47 and 48; in the form of relatively large airbubbles which are carried along by the stream from the propeller 47. Asthe entrained air bubbles pass, with 1 the stream, through the lowerpropeller 48 they are broken down to small bubbles which approach theideal bubble size of 0.20 cm. long axis diameter, for maximum aerationeffectiveness on sewage liquors undergoing treatment by the activatedsludge process, as set forth in detail in the aforementioned US. PatentNo. 2,928,661, and therefore need not be repeated here.

As stated in said patent, in applications involving very shallow liquidmasses, a single propeller may be sufficient, in which case theaspirator tubes are positioned above the single propeller so that thelarge air bubbles will be fined by passing through the propeller.

Referring again to FIGURE 2 it will be noted that there is no contactbetween the rapidly rotating hollow shaft 40-41 and the surfaces of theplug and its dependent nose 33. This spaced construction provides afriction free gas-tight joint between the shaft 41 and nose 33, thatcreates no power consuming drag on the shaft, thus making for loweroperating costs.

It will be further noted that due to the fact that the nose 33 of theair-inlet plug 30 extends downward beyond the open end of shaft 4041,any water carried along with the air passing through the nose bore 32will normally fall down the shaft 4041 and pass out through theaspirator tubes; and not travel back up the surface of the nose 33 andover into the shaft bearing bore 27.

If for any reason water vapor carried by the air should condense in theair-inlet plug bore 31 or shaft bore 27, in which the ball bearing 28 isseated, the negative pressure established in the air delivery system,due to the 4 aspirating effect of the rapidly rotating aspirating tubesand 46 carried by the shaft 40-41 will act to exhaust the condensatewithin a short time, leaving the parts dry.

Again, if for any reason, water should enter the system through thebreather 20, due to a driving rain or flooding of the area to a pointabove the level of the breather 20, the continued operation of theaspirator tubes will cause evaporation of any water that may seep intothe shaft bearing bore 27, leaving it dry before any corrosive actioncan occur.

Thus it will be obvious that my sewage aerator will continue to aeratethe sewage liquors undergoing treatment even though completelysubmerged, as long as the breather unit 20 is unobstructed. The presentdevice and invention is also susceptible of a broader use than theaeration of sewage. It may be used for chemical reactions such as thehalogenation of various organic materials, and the processing of foods,drugs, and cosmetics. The present device may also be used to aeratewater in fish hatcheries and it will also be appreciated that gasesother than air may be used or a combination of several gases.

Although this invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:

1. A flood-proof sewage aerator, comprising, a liquidtight electricmotor casing adapted to be mounted with its axis in a vertical planeabove the surface of sewage liquors undergoing treatment by theactivated sludge process in a sewage treatment tank; said casing havinga cylindrical side wall and upper and lower end walls joined thereto inliquid-tight sealed engagement; a stator in said casing; a hollow shaftrotatably supported within said casing through upper and lower bearingmeans mounted in the casing end walls; a rotor mounted on and carried bysaid hollow shaft; a cooling and lubricating oil partially filling saidcasing to completely submerge the stator and rotor; said hollow shafthaving an end portion extending downwardly from the casing, through anoil-tight seal mounted in the lower end wall, and projecting below thesurface of the mixed sewage liquors; a closure plug at the lowerterminal end of the hollow shaft; a screw-propeller mounted on the shaftat a point below the surface of the mixed sewage liquors; twodiametrically aligned aspirator tubes mounted on the hollow shaft,proximate the screw-propeller, and communicating with the interiorthereof; an air-inlet plug mounted through the casing upper end wall,above the upper shaft supporting bearing, in axial alignment with theopen upper end of the hollow shaft; said plug having a blind bore, of adiameter to fit snugly over the upper end of the hollow shaft; said plugalso having a dependent nose, centered in its blind bore, adapted toextend downwardly into the hollow shaft, and of a diameter to clear theinner wall thereof; the plug and nose having an axial bore therethroughconnecting the interior of the hollow shaft to the atmosphere, wherebyair is drawn through the hollow shaft, upon rapid rotation of theaspirator tubes mounted thereon, and injected into the mixed sewageliquors undergoing treatment.

2. A flood-proof sewage aerator, as in claim 1, wherein the hollow shafthas a second screw-propeller mounted proximate its closed end and sospaced from the first propeller that it will pick up the first propellercolumnated stream.

3. A flood-proof sewage aerator, as in claim 1, wherein the air-inletplug has an upstanding nipple through which its axial bore extends,adapted to be conected to an air delivery hose having air filteringmeans at its airinlet end.

4. A mixing device for applying gases to a liquid contained in atreatment tank which has generally liquid tight mounting means on topthereof including in combination a liquid tight motor casing mounted bysaid mounting means, an electric motor having a rotor and beingcontained in said casing and having an axis, bearing means carried bysaid casing, a shaft mounted by said bearing means, said shaftcomprising a downwardly extending extension of sufiicient length toreach liquid adapted to be contained in the treatment tank, wall meansin said shaft and extension defining a passage, conduit means connectingthe upper end of said passage to the outer wall of said mounting meansfor communication with a gas source, passage opening means in saidextension communicating at one end with said passage and extendingthrough the wall of said shaft extension to the outside thereof,aspirator tube means extending radially of said extension and being incommunication with said passage opening means, and propeller meanssecured to said shaft extension for mixing the liquid contained in thetreatment tank when said shaft is rotated, rotation of said shaftcausing aspirator action by said aspirator tube means and the drawing ofa gas through said conduit means, said passage and said passage openingmeans and into the liquid.

5. A sewage aerator for the treatment of sewage contained in a treatmenttank having an enclosure on top thereof including in combination a motorcasing mounted in the enclosure, an electric motor having a rotor andbeing contained in said casing and having an axis, bearing means carriedby said casing, a shaft mounted by said bearing means, said shaftcomprising a downwardly extending extension of suificient length toreach sewage adapted to be contained in the treatment tank, wall meansin said shaft and extension defining a passage, conduit means connectingthe upper end of said passage to the outer wall of said enclosure,aspirator passage means in said extension communicating at one end withsaid passage and extending through the wall of said shaft extension tothe outside thereof, aspirator tube means extending radially of saidextension and being in communication with said aspirator passage means,and screw means secured to said shaft extension for mixing sewagecontained in the treatment tank when said shaft is rotated, rotation ofsaid shaft causing aspirator action by said aspirator tube means and thedrawing of air through said passage and conduit means and into thesewage, an annular housing surrounding the top of said shaft, saidconduit means comprising a fitting having a nose portion which extendsinto the top of said passage in said shaft in a non-engaging manner andwhich fitting has an outer portion extending between said annularhousing and the top of said shaft and is threadably secured to saidannular housing, and a flexible conduit connects to said fitting at oneend and at its other end communicates with atmosphere through an openingin the enclosure.

References Cited UNITED STATES PATENTS 1,819,637 8/1931 Carlson et a1261--87 X 2,928,661 3/1960 MacLaren 261-24 2,996,287 8/1961 Audran26'187 X 3,053,390 9/1962 Wood 26193 X 3,119,779 1/1964 Barrows et a1261-87 X 3,279,768 10/1966 Niewiarowicz 26'1-93 X FOREIGN PATENTS448,852 6/1936 Great Britain.

0 HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner.

